1. Field of Invention
The present invention relates generally to the field of solids deposition on surfaces, and more particularly to apparatus and methods for producing layers of solids deposits under continuous flow conditions as a function of influencing variables including, but not limited to flow rate, temperature, pressure, shear, surface type, surface roughness, chemical inhibitors and chemical inducers. The apparatus and methods are useful for predicting solids deposition from fluids including, but not limited to reservoir hydrocarbon and aqueous based fluids, drilling muds, frac fluids, emulsions, and the like, which may have multiple phases (solid, liquid, gas, and combinations thereof).
2. Related Art
Oil fields flow assurance characterizes the operability and reliability of oil and/or gas production systems. Organic and inorganic solids (wax, asphaltenes, hydrates, scale, and the like) precipitation, deposition, emulsion, foaming, corrosion, erosion, inhibition, rheology, and complex multi-phase flow are some of the key issues related to flow assurance. Many flow problems are due to hydrates, wax, asphaltene and scale precipitation, which may lead to deposition on internal pipe and other equipment surfaces, causing pressure reduction, slower production, and ultimately plugging. Moreover, elevated viscosity at low temperatures (gelling) represents potential rheological problems, which may lead to slugging.
One aspect of “flow assurance” is managing the precipitation and deposition formation of these solids: wax, asphaltene, scales, hydrates, among many others. Even though solids precipitation is a prelude to solids deposition, their presence can be passive if proper measures are taken to avoid their adhesiveness to surfaces. It is now proven that any solids deposition occurrence can be a function of any of the following parameters: composition, viscosity, production rate, system pressure, system temperatures, and presence of water, deposition surface type and deposition surface roughness. Solutions to remediate the deposition problem vary from mechanical design to chemical injection. The economic implication, if wrong assessments are made, can be very serious and lead to significant losses due to slow production or shut down. Even though the subject of oil production has been well investigated, the tools to predict and conceptually design the production system, including pipelines, based on reliable experimental measurements and evaluation are very few. So far, very limited and unreliable experimental predictive methods and approaches are available to assess and quantify the wax deposition process, especially under various actual pipeline conditions and/or reservoir conditions. Most available methods fall short in mimicking the actual pipeline turbulent conditions in general, especially at relatively high Reynolds number and high shear. For the asphaltene deposition process, only one known tool, known under the trade designation OSDC (discussed below) is available to trigger and measure deposition under real pipelines conditions of shear, pressure and temperature. There are no known tools or devices available to evaluate, predict, measure or produce scale and hydrates deposits under transport conditions whether at steady state or transient.
Schlumberger has used the system known as the Organic Solids Deposition and Control system (OSDC), described more fully in U.S. Pat. Nos. 6,959,588 and 7,150,183, to identify, produce and control both wax and asphaltene deposits at very realistic reservoir as well as transport conditions. The experimental results using the system known as OSDC were benchmarked against field data and were found to be conservative, yet superior when compared to any other methods such as flow loops, cold finger and stirring tanks. Feedback from major oil companies was very encouraging. The experimental data from live oils, which are expensive to sample, are invaluable.
Despite success of the apparatus known under the trade designation OSDC, the system has numerous limitations in terms of being capable to meet the fast-growing and continuously evolving market. The high cost of the live oil sample collection and its uniqueness make it challenging and crucial for the industry to minimize the risks of not only losing the sample, but most importantly to extract the maximum information possible from it. Better controllability, more powerful hardware, improved design and enhanced geometry are desired to achieve ideal data quality and greater profitability.